The only potential problem is that there was a test done that showed the squares were not as evenly dosed as originally claimed. However, if you are taking more than a square in a day everything should even out.
The tests showed that they were dosed between 8-9mg per square or so. The manufactur has stated that he has now added 10-15% more chem to the paper. New tests are coming out but I believe them to be overdosed by each square.